Midwave infrared (MWIR) photodetectors have recently been developed using an nBn structure which employs a barrier (B) to block the flow of majority carrier current while allowing the flow of minority carriers (see e.g. U.S. Pat. No. 7,687,871). Such nBn photodetectors, which employ a single light-absorbing layer of indium arsenide (InAs) have a long cutoff wavelength of 3.4 microns (μm) for the detection of MWIR light. The use of indium arsenide antimonide (InAsSb) for the light-absorbing layer allows the long cutoff wavelength to be extended to about 4.2 μm.
The present invention provides an advance in the art of nBn photodetectors by providing a plurality of InAsSb light-absorbing layers with tensile-strained layers interspersed therebetween. The tensile-strained layers can comprise gallium arsenide (GaAs), indium arsenide (InAs), indium gallium arsenide (InGaAs), or a combination of these III-V compound semiconductors. By providing the tensile-strained layers interspersed between the InAsSb light-absorbing layers according to the present invention, the amount of antimony in the InAsSb light-absorbing layers can be increased; and this allows the long cutoff wavelength to be increased beyond the present limit to 4.5-10 μm at a temperature of 160 K or less.
These and other advantages of the present invention will become evident to those skilled in the art.